More friendly error msg; Fix Android Demo LLVM ver (#3962)

CMakeLists.txt

@@ -101,7 +101,7 @@ else(MSVC)
     set(CMAKE_C_FLAGS "-O2 -Wall -fPIC ${CMAKE_C_FLAGS}")
     set(CMAKE_CXX_FLAGS "-O2 -Wall -fPIC ${CMAKE_CXX_FLAGS}")
     if (HIDE_PRIVATE_SYMBOLS)
-      message("Hide private symbols...")
+      message(STATUS "Hide private symbols...")
       set(CMAKE_C_FLAGS "-fvisibility=hidden ${CMAKE_C_FLAGS}")
       set(CMAKE_CXX_FLAGS "-fvisibility=hidden ${CMAKE_CXX_FLAGS}")
     endif(HIDE_PRIVATE_SYMBOLS)

cmake/util/FindLLVM.cmake

@@ -49,13 +49,29 @@ macro(find_llvm use_llvm)
     message(STATUS "Use llvm-config=" ${LLVM_CONFIG})
     separate_arguments(LLVM_CONFIG)
     execute_process(COMMAND ${LLVM_CONFIG} --libfiles
+      RESULT_VARIABLE __llvm_exit_code
       OUTPUT_VARIABLE __llvm_libfiles)
+    if(NOT "${__llvm_exit_code}" STREQUAL "0")
+      message(FATAL_ERROR "Fatal error executing: ${use_llvm} --libfiles")
+    endif()
     execute_process(COMMAND ${LLVM_CONFIG} --system-libs
+      RESULT_VARIABLE __llvm_exit_code
       OUTPUT_VARIABLE __llvm_system_libs)
+    if(NOT "${__llvm_exit_code}" STREQUAL "0")
+      message(FATAL_ERROR "Fatal error executing: ${use_llvm} --system-libs")
+    endif()
     execute_process(COMMAND ${LLVM_CONFIG} --cxxflags
+      RESULT_VARIABLE __llvm_exit_code
       OUTPUT_VARIABLE __llvm_cxxflags)
+    if(NOT "${__llvm_exit_code}" STREQUAL "0")
+      message(FATAL_ERROR "Fatal error executing: ${use_llvm} --cxxflags")
+    endif()
     execute_process(COMMAND ${LLVM_CONFIG} --version
+      RESULT_VARIABLE __llvm_exit_code
       OUTPUT_VARIABLE __llvm_version)
+    if(NOT "${__llvm_exit_code}" STREQUAL "0")
+      message(FATAL_ERROR "Fatal error executing: ${use_llvm} --version")
+    endif()
     # llvm version
     string(REGEX REPLACE "^([^.]+)\.([^.])+\.[^.]+.*$" "\\1\\2" TVM_LLVM_VERSION ${__llvm_version})
     # definitions

docker/Dockerfile.demo_android

@@ -61,7 +61,7 @@ RUN cd /usr && \
     mkdir -p build && \
     cd build && \
     cmake \
-        -DUSE_LLVM=llvm-config-6.0 \
+        -DUSE_LLVM=llvm-config-8 \
         -DUSE_RPC=ON \
         -DUSE_SORT=ON \
         -DUSE_GRAPH_RUNTIME=ON \

tutorials/frontend/deploy_model_on_android.py

@@ -66,7 +66,7 @@ from tvm.contrib.download import download_testdata
 #
 #   mkdir build
 #   cd build
-#   cmake -DUSE_LLVM=llvm-config-6.0 \
+#   cmake -DUSE_LLVM=llvm-config-8 \
 #         -DUSE_RPC=ON \
 #         -DUSE_SORT=ON \
 #         -DUSE_VULKAN=ON \